Prior art antennas include:                (1) Flared notch type antennas, which are capable of somewhat broadband operation, but are typically limited to a bandwidth between 3:1 and 10:1. The antenna of the presently disclosed technology uses a long slot array that is capable of much broader bandwidth, approaching 100:1.        (2) Spiral antennas or log-periodic antennas, which are difficult to build into arrays because of their size. The result is that they have low aperture efficiency at high frequencies.        (3) Traditional phase shifters or true-time-delay elements. Phase shifters naturally cannot achieve broad bandwidth. True-time-delay elements can achieve broad bandwidth, but if an individual device is connected to each antenna, the resulting array is complex and expensive. The disclosed beam former uses a quasi-optical technique, resulting in a much simpler beam former.        (4) Traditional quasi-optical techniques. These are typically very large due to the need for lens-like structures. The disclosed quasi-optical technique uses a unique folded lens, so the resulting structure is much smaller.        (5) Parallel plate Luneberg lenses. See “Angular Independency of a Parallel-Plate Luneberg Lens With Hexagonal Lattice and Circular Metal Posts” by Yosang-Jin Park and Werner Wiesbeck, IEEE Antennas and Wireless Progation Lett., Vol. 1, 2002.        
Artificial dielectric materials are also known in the art. See my U.S. patents:                (1) U.S. Pat. No. 6,518,931 “Vivaldi cloverleaf antenna”        (2) U.S. Pat. No. 6,496,155 “End-fire antenna or array on surface with tunable impedance”        (3) U.S. Pat. No. 6,483,481 “Textured surface having high electromagnetic impedance in multiple frequency bands”        (4) U.S. Pat. No. 6,483,480 “Tunable impedance surface”        (5) U.S. Pat. No. 6,433,756 “Method of providing increased low-angle radiation sensitivity in an antenna and an antenna having increased low-angle radiation sensitivity”        (6) U.S. Pat. No. 6,426,722 “Polarization converting radio frequency reflecting surface”        (7) U.S. Pat. No. 6,384,797 “Reconfigurable antenna for multiple band, beam-switching operation”        (8) U.S. Pat. No. 6,366,254 “Planar antenna with switched beam diversity for interference reduction in a mobile environment”        (9) U.S. Pat. No. 6,262,495 “Circuit and method for eliminating surface currents on metals”the disclosures of which patents are hereby incorporated herein by reference.        
This disclosed technology relates to antennas and beam formers, which are capable of ultra broad bandwidth (approaching 100:1) and beam switching. The disclosed antenna can achieve much broader bandwidth and smaller size than existing approaches by combining a broadband long slot aperture with a folded quasi-optical beam former. The disclosed antenna can be used for (i) broadband communication systems, such as impulse radio, (ii) broadband listening systems, or (iii) impulse radar. It can also be used in both military and civilian applications such as collision avoidance radar applications.